1. Technical Field
The present invention relates to cognitive radio systems, and, in particular, to methods and systems for detecting unused channels in a cognitive radio system.
2. Description of the Related Art
Cognitive radio (CR) is a promising technology that can significantly improve spectrum utilization. One important aspect of CR systems is spectrum sensing, which is a research subject that has recently gained considerable interest. Most existing work on spectrum sensing has focused on a narrow-band single-channel scenario. Very recently, wide-band spectrum sensing has been studied especially for orthogonal frequency division multiplexing (OFDM) CR systems. In these works, multiple sensors (detectors), each for a channel, are needed to simultaneously observe multi-channels in an OFDM system. In addition, multi-channel joint energy detection and sequential detection schemes have been developed in an attempt to maximize overall throughput performance. Under this setting, a large number of sensors (detectors) are required when the number of subchannels in an OFDM system is large, and simultaneous operation of these sensors is also needed. However, it is often practically difficult for a CR system to equip a large number of detection sensors and operate them simultaneously.